With the increasing growth of color photographic light-sensitive materials, color processing of color photographic materials is more and more simplified and quickened. On the other hand, high quality color images and uniformity of finished image quality have been required. It is known that a silver iodobromide emulsion containing from 4 to 20 mol % silver iodide is generally used for photographing color photographic materials and a silver chlorobromide emulsion is generally used for color photographic papers for printing. It is also known that a silver chlorobromide is reluctant to give images having high quality at high speed as compared to a silver iodobromide emulsion.
Silver chlorides or silver chlorobromide of, in particular, cubic grains having a (100) crystal plane are very useful for rapid simple processing. However, they have the disadvantages that the sensitivity thereof is low, chemical sensitization and spectral sensitization are not easily achieved, the sensitivity obtained is unsuitable, and the silver halide grains have a tendency to produce fog.
Various methods for solving these problems have been proposed. For example, a method of adding water-soluable bromide ions or iodide ions to the silver halide emulsion after adding sensitizing dye(s) thereto is described in Japanese Patent Application (OPI) No. 51627/73 (The term "OPI" as used herein means an "unexamined published application".), Japanese Patent Publication No. 46932/74, etc.; a method of simultaneously adding bromide ions and silver ions to silver halide grains having a high content of silver chloride to form a silver bromide region of more than 60 mol % on the surface of the grains or of similarly forming a layer of 10 mol % to 50 mol % silver bromide on the surface of the grains is described in Japanese Patent Application (OPI) Nos. 108533/83, 222845/85, etc.; and a method of adding bromide ions or simultaneously adding bromide ions and silver ions to silver halide grains having a high content of silver chloride to form, thus, multiphase structure grains such as double layer grains or junction structure grains is described in Japanese Patent Publication Nos. 36978/75, 240772/83, U.S. Pat. No. 4,471,050, West German Patent Application (OLS) No. 3,229,999, etc.
However, all of the aforesaid methods have been found to have various defects in terms of sensitivity and have stability thereof, in particular, a reduction in sensitivity by the addition of color couplers to the silver halide grains, and on the tightness of gradation at shadow portions. Also, it is known that these silver halide emulsions are unstable and thus the production thereof is difficult. This matter is described, for example, in Zuckerman Journal of Photographic Science, 24, 142(1976), etc.